1. Field of the Invention
The present invention relates to a fan arranged to produce air currents.
2. Description of the Related Art
Fans have often been used as cooling fans arranged to cool electronic components inside cases of a variety of electronic devices. A motor portion of a blower fan disclosed in JP-A 2009-213225 includes a base portion, an armature, a substantially cylindrical bearing support portion, two ball bearings, and a rotor portion. The bearing support portion is fixed in a center of the base portion. The two ball bearings are fixed to an inside surface of the bearing support portion, while the armature is fixed to an outside surface of the bearing support portion. A shaft is inserted in the ball bearings, so that the rotor portion is supported to be rotatable with respect to the bearing support portion. The base portion includes an annular groove defined therein which is arranged to surround a circumference of the bearing support portion. A helical coil spring is disposed in this groove. An upper end portion of the coil spring is arranged to be in axial contact with an insulator of the armature. Thus, vibrations of the armature are absorbed by the coil spring during rotation of the rotor portion, so that vibrations of the blower fan are reduced.
A bearing apparatus used in a spindle motor disclosed in JP-A 2005-155912 includes a shaft, a thrust plate, a sleeve, and a housing arranged in the shape of a cylinder with a bottom. The shaft is inserted in the sleeve. The housing is arranged to accommodate the sleeve. The thrust plate is arranged at a lower end portion of the shaft. An inner circumferential surface of the sleeve includes dynamic pressure generating grooves defined therein, and a radial dynamic pressure bearing is defined between an outer circumferential surface of the shaft and the inner circumferential surface of the sleeve. Each of a lower end surface of the sleeve and an upper surface of a bottom portion of the housing includes thrust dynamic pressure generating grooves defined therein. Thrust dynamic pressure bearings are defined between the lower end surface of the sleeve and an upper surface of the thrust plate, and between a lower surface of the thrust plate and the upper surface of the bottom portion of the housing.
A cooling fan disclosed in US 2008/0278911 includes a base portion, a bearing portion, a fluid dynamic bearing, a coil assembly, and an impeller.